Kotlin DSA Series — Complete Index

Posted May 30, 2026 Updated Jun 29, 2026

By TalkTechie

6 min read

A complete Data Structures & Algorithms series written in idiomatic Kotlin. Not Java translated to .kt — real Kotlin the way it’s meant to be written.

🟢 Phase 1 — Arrays & Hashing

LC #	Problem	Difficulty	Post
#1	Two Sum	Easy	Read →
#121	Best Time to Buy and Sell Stock	Easy	Read →
#217	Contains Duplicate	Easy	Read →
#242	Valid Anagram	Easy	Read →
#238	Product of Array Except Self	Medium	Read →
#53	Maximum Subarray	Medium	Read →
#49	Group Anagrams	Medium	Read →
#347	Top K Frequent Elements	Medium	Read →
#271	Encode and Decode Strings	Medium	Read →
#36	Valid Sudoku	Medium	Read →
#128	Longest Consecutive Sequence	Medium	Read →

🟡 Phase 2 — Two Pointers

LC #	Problem	Difficulty	Post
#125	Valid Palindrome	Easy	Read →
#167	Two Sum II — Input Array Is Sorted	Medium	Read →
#15	3Sum	Medium	Read →
#11	Container With Most Water	Medium	Read →
#42	Trapping Rain Water	Hard	Read →

🟠 Phase 3 — Stack

LC #	Problem	Difficulty	Post
#20	Valid Parentheses	Easy	Read →
#155	Min Stack	Medium	Read →
#150	Evaluate Reverse Polish Notation	Medium	Read →
#739	Daily Temperatures	Medium	Read →
#853	Car Fleet	Medium	Read →
#84	Largest Rectangle In Histogram	Hard	Read →

🔵 Phase 4 — Binary Search

LC #	Problem	Difficulty	Post
#704	Binary Search	Easy	Read →
#74	Search a 2D Matrix	Medium	Read →
#875	Koko Eating Bananas	Medium	Read →
#153	Find Minimum In Rotated Sorted Array	Medium	Read →
#33	Search In Rotated Sorted Array	Medium	Read →
#981	Time Based Key-Value Store	Medium	Read →
#4	Median of Two Sorted Arrays	Hard	Read →

🟣 Phase 5 — Sliding Window

LC #	Problem	Difficulty	Post
#121	Best Time to Buy And Sell Stock	Easy	Read →
#3	Longest Substring Without Repeating Characters	Medium	Read →
#424	Longest Repeating Character Replacement	Medium	Read →
#567	Permutation In String	Medium	Read →
#76	Minimum Window Substring	Hard	Read →
#239	Sliding Window Maximum	Hard	Read →

🟢 Phase 6 — Linked List

LC #	Problem	Difficulty	Post
#206	Reverse Linked List	Easy	Read →
#21	Merge Two Sorted Lists	Easy	Read →
#141	Linked List Cycle	Easy	Read →
#143	Reorder List	Medium	Read →
#19	Remove Nth Node From End of List	Medium	Read →
#138	Copy List With Random Pointer	Medium	Read →
#2	Add Two Numbers	Medium	Read →
#287	Find The Duplicate Number	Medium	Read →
#146	LRU Cache	Medium	Read →
#23	Merge K Sorted Lists	Hard	Read →
#25	Reverse Nodes In K-Group	Hard	Read →

🔴 Phase 7 — Trees

LC #	Problem	Difficulty	Post
#226	Invert Binary Tree	Easy	Read →
#104	Maximum Depth of Binary Tree	Easy	Read →
#543	Diameter of Binary Tree	Easy	Read →
#110	Balanced Binary Tree	Easy	Read →
#100	Same Tree	Easy	Read →
#572	Subtree of Another Tree	Easy	Read →
#235	Lowest Common Ancestor of a Binary Search Tree	Medium	Read →
#102	Binary Tree Level Order Traversal	Medium	Read →
#199	Binary Tree Right Side View	Medium	Read →
#1448	Count Good Nodes In Binary Tree	Medium	Read →
#98	Validate Binary Search Tree	Medium	Read →
#230	Kth Smallest Element In a BST	Medium	Read →
#105	Construct Binary Tree From Preorder And Inorder Traversal	Medium	Read →
#124	Binary Tree Maximum Path Sum	Hard	Read →
#297	Serialize And Deserialize Binary Tree	Hard	Read →

🟤 Phase 8 — Trie

LC #	Problem	Difficulty	Post
#208	Implement Trie (Prefix Tree)	Medium	Read →
#211	Design Add And Search Words Data Structure	Medium	Read →
#212	Word Search II	Hard	Read →

⚪ Phase 9 — Heap / Priority Queue

LC #	Problem	Difficulty	Post
#703	Kth Largest Element In a Stream	Easy	Read →
#1046	Last Stone Weight	Easy	Read →
#973	K Closest Points to Origin	Medium	Read →
#215	Kth Largest Element In An Array	Medium	Read →
#621	Task Scheduler	Medium	Read →
#355	Design Twitter	Medium	Read →
#295	Find Median From Data Stream	Hard	Read →

🟢 Phase 10 — Backtracking

LC #	Problem	Difficulty	Post
#78	Subsets	Medium	Read →
#39	Combination Sum	Medium	Read →
#40	Combination Sum II	Medium	Read →
#46	Permutations	Medium	Read →
#90	Subsets II	Medium	Read →
#22	Generate Parentheses	Medium	Read →
#79	Word Search	Medium	Read →
#131	Palindrome Partitioning	Medium	Read →
#17	Letter Combinations of a Phone Number	Medium	Read →
#51	N Queens	Hard	Read →

🔵 Phase 11 — Graphs

LC #	Problem	Difficulty	Post
#200	Number of Islands	Medium	Read →
#695	Max Area of Island	Medium	Read →
#133	Clone Graph	Medium	Read →
#286	Walls And Gates	Medium	Read →
#994	Rotting Oranges	Medium	Read →
#417	Pacific Atlantic Water Flow	Medium	Read →
#130	Surrounded Regions	Medium	Read →
#207	Course Schedule	Medium	Read →
#210	Course Schedule II	Medium	Read →
#261	Graph Valid Tree	Medium	Read →
#323	Number of Connected Components In An Undirected Graph	Medium	Read →
#684	Redundant Connection	Medium	Read →
#127	Word Ladder	Hard	Read →

🟡 Phase 12 - 1-D Dynamic Programming

LC #	Problem	Difficulty	Post
#70	Climbing Stairs	Easy	Read →
#746	Min Cost Climbing Stairs	Easy	Read →
#198	House Robber	Medium	Read →
#213	House Robber II	Medium	Read →
#5	Longest Palindromic Substring	Medium	Read →
#647	Palindromic Substrings	Medium	Read →
#91	Decode Ways	Medium	Read →
#322	Coin Change	Medium	Read →
#152	Maximum Product Subarray	Medium	Read →
#139	Word Break	Medium	Read →
#300	Longest Increasing Subsequence	Medium	Read →
#416	Partition Equal Subset Sum	Medium	Read →

🔶 Phase 13 - Intervals

LC #	Problem	Difficulty	Post
#57	Insert Interval	Medium	Read →
#56	Merge Intervals	Medium	Read →
#435	Non Overlapping Intervals	Medium	Read →
#252	Meeting Rooms	Easy	Read →
#253	Meeting Rooms II	Medium	Read →
#1851	Minimum Interval to Include Each Query	Hard	Read →

🟣 Phase 14 - Greedy

LC #	Problem	Difficulty	Post
#53	Maximum Subarray	Medium	Read →
#55	Jump Game	Medium	Read →
#45	Jump Game II	Medium	Read →
#134	Gas Station	Medium	Read →
#846	Hand of Straights	Medium	Read →
#2382	Merge Triplets to Form Target Triplet	Medium	Read →
#763	Partition Labels	Medium	Read →
#678	Valid Parenthesis String	Medium	Read →

🟠 Phase 15 - Advanced Graphs

LC #	Problem	Difficulty	Post
#743	Network Delay Time	Medium	Read →
#332	Reconstruct Itinerary	Hard	Read →
#1584	Min Cost to Connect All Points	Medium	Read →
#778	Swim In Rising Water	Hard	Read →
#269	Alien Dictionary	Hard	Read →
#787	Cheapest Flights Within K Stops	Medium	Read →

🟤 Phase 16 - 2-D Dynamic Programming

LC #	Problem	Difficulty	Post
#62	Unique Paths	Medium	Read →
#1143	Longest Common Subsequence	Medium	Read →
#309	Best Time to Buy And Sell Stock With Cooldown	Medium	Read →
#518	Coin Change II	Medium	Read →
#494	Target Sum	Medium	Read →
#97	Interleaving String	Medium	Read →
#329	Longest Increasing Path In a Matrix	Hard	Read →
#115	Distinct Subsequences	Hard	Read →
#72	Edit Distance	Medium	Read →
#312	Burst Balloons	Hard	Read →
#10	Regular Expression Matching	Hard	Read →

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Kotlin DSA, Index

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